1. Field of the Invention
The present invention relates to a method of receiving system information for a wireless communications system and related communications device, and more particularly to a method of receiving modification indication of system information for a user equipment in a CELL_PCH state in a wireless communications system and related communications device.
2. Description of the Prior Art
The third generation (3G) mobile telecommunications system has adopted a Wideband Code Division Multiple Access (WCDMA) wireless air interface access method for a cellular network. WCDMA provides high frequency spectrum utilization, universal coverage, and high quality, high-speed multimedia data transmission. The WCDMA method also meets all kinds of QoS requirements simultaneously, providing diverse, flexible, two-way transmission services and better communication quality to reduce transmission interruption rates. Through the 3G mobile telecommunications system, a user can utilize a wireless communications device, such as a mobile phone, to realize real-time video communications, conference calls, real-time games, online music broadcasts, and email sending/receiving. However, these functions rely on fast, instantaneous transmission. Thus, targeting at the third generation mobile telecommunication technology, the 3rd Generation Partnership Project (3GPP) provides High Speed Package Access (HSPA) technology, which includes High Speed Downlink Package Access (HSDPA) and High Speed Uplink Package Access (HSUPA), to increase bandwidth utility rate and package data processing efficiency to improve uplink/downlink transmission rate.
On the basis of HSDPA, the 3GPP further introduces HS-DSCH (High Speed Downlink Shared Channel) reception in a CELL_PCH and a URA-PCH state, allowing the UE in the CELL_PCH or the URA-PCH state to monitor an HS-DSCH accompanied with a Shared Control Channel for HS-DSCH (HS-SCCH) for downlink data reception, so as to improve a peak data rate, a signaling delay, a state transition delay, download times and flexible cell capacity. In the HS-DSCH reception in the CELL_PCH and URA_PCH state, the HS-DSCH is a transport channel allowed to map on dedicated-type logic channels including a Dedicated Control Channel (DCCH) and a Dedicated Traffic Channel (DTCH) or common-type logic channels including a Paging Control Channel (PCCH) and a Broadcast Control Channel (BCCH).
A UMTS radio access network (UTRAN) enables the HS-DSCH reception in the CELL_PCH and the URA_PCH state by including parameters, related to radio resource control (RRC) configuration of PICH (Paging Indicator Channel), HS-SCCH, HS-DSCH and an H-RNTI (HS-DSCH radio network transaction identifier) for PCCH transmission, in the system information broadcast. The parameters are configured in a “HS-DSCH paging system information” information element (IE) included in a system information block (SIB) type 5/5bis sent from the UTRAN to the UE.
During performance of the HS-DSCH reception in the CELL_PCH and the URA_PCH state, the UE may use a common or a dedicated H-RNTI as a UE identity for reception of HS-DSCH packets.
The common H-RNTI can be shared by multiple UEs, whereas each dedicated H-RNTI is only allocated to one UE. During reception of downlink media access control (MAC) packets, the UE using the common H-RNTI needs to determine whether the received packets are of its own with UE identification information (i.e. UE ID and UE ID Type) in the packet header. On the other hand, the MAC packets for the UE using the dedicated H-RNTI include no UE identification information to provide better data transmission efficiency. As a result, PCCH reception requires the common H-RNTI, and DCCH and DTCH receptions require the dedicated H-RNTI. Furthermore, with the available HS-DSCH reception, the UE using the dedicated H-RNTI in the CELL_PCH state can perform downlink and uplink data transmissions without a cell update procedure.
When the UTRAN allocates a dedicated H-RNTI to the UE, the UE stores the dedicated H-RNTI in an H-RNTI variable. In addition, when the UE is in the CELL_PCH state and the SIB type 5/5bis includes the “HS-DSCH paging system information” IE, the UE has to use the dedicated H-RNTI for the HS-DSCH reception if the H-RNTI variable is set, otherwise the UE selects the common H-RNTI to use from the “HS-DSCH paging system information” IE.
A PAGING TYPE 1 and a PAGING TYPE 2 message are RRC messages provided in the related RRC specification for paging operation. The former is applied to the UE in an idle mode, a CELL_PCH state, or a URA_PCH sate and sent on the PCCH for notifying the UE of general paging information corresponding to modification indication of SIBs or a terminating call. The latter is applied to the UE in a CELL_FACH or a CELL_DCH state and sent on DCCH for notifying the UE of dedicated paging information.
When the SIB configuration needs to be modified, the UTRAN includes a “BCCH modification info” IE in the PAGING TYPE 1 message and sends the PAGING TYPE 1 message on the PCCH. However, the UE selects either the common or dedicated H-RNTI to use according to the state of the H-RNTI variable. That is to say, the UE cannot use the common and dedicated H-RNTIs simultaneously. Consequently, the UE using the dedicated H-RNTI cannot receive the PAGING TYPE 1 message sent on the PCCH.
According to the prior art, a UE in the CELL_PCH state counts on the paging information on the PCCH for the modification indication of the SIBs. But the UE using the dedicated H-RNTI in the CELL_PCH state cannot receive any paging information on the PCCH, possibly resulting in a connection loss between the UE and the UTRAN.